Using sheets of light to corral waves of ultracold atoms, researchers have created an experimental platform for studying the event horizons of black holes.
According to theory, if a pair of mirrors facing one another is vibrated rapidly enough, the optical field between them will display black-hole-like traits, such as the equivalent of an event horizon. These conditions have not yet been realized in the lab, but now researchers have managed something similar by swapping the roles of light and matter [1]. They used sheets of light to reflect waves of ultracold atoms back and forth, creating what they call a matter-wave cavity. Vibrating the sheets of light allows them to simulate the behavior of light propagating close to a black hole, while their setup could also enable the study of many other exotic phenomena.
An optical cavity, which is formed by a pair of mirrors facing one another, offers a versatile tool for manipulating light. Vibrating one of the mirrors causes the length of the cavity to oscillate, which can alter the light’s properties. If the mirror could be made to oscillate at the cavity’s resonant frequency—which would require motion at close to the speed of light—all the light would be compressed into an extremely short, intense pulse that would bounce between the mirrors.